It is known from GB patent 2 234 723 to Crafer to provide a wing sail including solar collectors mounted thereon. More particularly, the Crafer patent discloses a multi-hull waterborne craft including an assembly of three wing sails, each wing sail being rotatable in concert about its longitudinal axis and the assembly of wing sails itself rotatable about a vertical axis coincident with the longitudinal axis of the middle wing sail. For stowage, the assembly of wing sails can be rotated to a line abeam configuration at which the assembly can then be stowed by pivoting the assembly about a horizontal abeam axis to lie the assembly down on the deck of the craft.